A field kinetic coupling with the Einstein tensor leads to a gravitationally enhanced friction during inflation, by which even steep potentials with theoretically natural model parameters can drive cosmic acceleration. In the presence of this nonminimal derivative coupling, we place observational constraints on a number of representative inflationary models such as chaotic inflation, inflation with exponential potentials, natural inflation, and hybrid inflation. We show that most of the models can be made compatible with the current observational data mainly due to the suppressed tensor-to-scalar ratio.

We use cosmic microwave background data from the WMAP, SPT, BICEP, and QUaD experiments to obtain constraints on the dark matter particle mass $m_{\chi }$, and show that the combined data requires $m_{\chi }>7.6\mathrm{GeV}$ at the 95% confidence level for the $\chi \chi \to b\overline{b}$ channel assuming $s$-wave annihilation and a thermal cross section $⟨{\sigma }_{\mathrm{a}}v⟩=3\times {10}^{-26}{\mathrm{cm}}^3/\mathrm{s}$. We examine whether the bound on $m_{\chi }$ is sensitive to ${\sigma }_8$ measurements made by galaxy cluster observations. The large uncertainty in ${\sigma }_8$ and the degeneracy with ${\Omega }_{\mathrm{m}}$ allow only small improvements in the dark matter mass bound. Increasing the number of effective neutrinolike degrees of freedom to $N_{\mathrm{eff}}=3.85$ improves the mass bound to $m_{\chi }>8.6\mathrm{GeV}$ at 95% confidence, for the $\chi \chi \to b\overline{b}$ channel. We also study models in which dark matter halos at $z<60$ reionize the Universe. We compute the Ostriker-Vishniac power resulting from partial reionization at intermediate redshifts $10<z<60$, but find the effect to be small. We discuss the importance of the large angle polarization as a complementary probe of dark matter annihilation. By performing Monte Carlo simulations, we show that future experiments that measure the $EE$ power spectrum from $20<l<50$ can exclude $m_{\chi }\sim 10\mathrm{GeV}$ at the $2(3)\sigma$ level provided the error bars are smaller than $4(3)\times \mathrm{\text{cosmic variance}}$. We show that the Planck experiment will significantly improve our knowledge of dark matter properties.

Cosmic bubble collisions provide an important possible observational window on the dynamics of eternal inflation. In eternal inflation, our observable universe is contained in one of many bubbles formed from an inflating metastable vacuum. The collision between bubbles can leave a detectable imprint on the cosmic microwave background radiation. Although phenomenological models of the observational signature have been proposed, to make the theory fully predictive one must determine the bubble collision spacetime, and thus the cosmological observables, from a scalar field theory giving rise to eternal inflation. Because of the intrinsically nonlinear nature of the bubbles and their collision, this requires a numerical treatment incorporating General Relativity. In this paper, we present results from numerical simulations of bubble collisions in full General Relativity. These simulations allow us to accurately determine the outcome of bubble collisions, and examine their effect on the cosmology inside a bubble universe. We confirm the validity of a number of approximations used in previous analytic work, and identify qualitatively new features of bubble collision spacetimes. Both vacuum bubbles and bubbles containing a realistic inflationary cosmology are studied. We identify the constraints on the scalar field potential that must be satisfied in order to obtain collisions that are consistent with our observed cosmology, yet leave detectable signatures.

We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo observations between July 7, 2009, and October 20, 2010. We searched for signals from binaries with total mass between 2 and $25M_{\odot }$; this includes binary neutron stars, binary black holes, and binaries consisting of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass, including the results from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are $1.3\times {10}^{-4}$, $3.1\times {10}^{-5}$, and $6.4\times {10}^{-6}{\mathrm{Mpc}}^{-3}{\mathrm{yr}}^{-1}$, respectively. These upper limits are up to a factor 1.4 lower than previously derived limits. We also report on results from a blind injection challenge.

We demonstrate entanglement generation between mode pairs of a quantum field in a single, rigid cavity that moves nonuniformly in Minkowski space-time. The effect is sensitive to the initial state, the choice of the mode pair and bosonic versus fermionic statistics, and it can be stronger by orders of magnitude than the entanglement degradation between an inertial cavity and a nonuniformly moving cavity. Detailed results are given for massless scalar and spinor fields in ($1+1$) dimensions. By the equivalence principle, the results model entanglement generation by gravitational effects.

In order to explain the Tevatron anomaly of the top quark forward-backward asymmetry $A_{\mathrm{FB}}^t$ in the left-right twin Higgs model, we choose to give up the lightest neutral particle of $\widehat{h}$ field as a stable dark matter candidate. Then a new Yukawa interaction for $\widehat{h}$ is allowed, which can be free from the constraint of same-sign top pair production and contribute sizably to $A_{\mathrm{FB}}^t$. Considering the constraints from the production rates of the top pair ($t\overline{t}$), the top decay rates, and $t\overline{t}$ invariant mass distribution, we find that this model with such new Yukawa interaction can explain $A_{\mathrm{FB}}^t$ measured at the Tevatron while satisfying the charge asymmetry $A_C^t$ measured at the LHC. Moreover, this model predicts a strong correlation between $A_C^t$ at the LHC and $A_{\mathrm{FB}}^t$ at the Tevatron, i.e., $A_C^t$ increases as $A_{\mathrm{FB}}^t$ increases.

We study the associated production of a charged Higgs and a $W$ boson in high-energy $pp$ collisions at the LHC. This is an interesting process for charged Higgs discovery, or exclusion, since the production cross section could depend strongly on the model, offering potential discriminating power between supersymmetric extensions of the standard model with minimal or extended Higgs sectors. We compute the cross section for this process in the next-to-minimal supersymmetric standard model (NMSSM), at the tree level for quark-quark scattering, and at one-loop level for gluon-gluon scattering. The most important corrections beyond leading order are taken into account using an improved Born approximation. We find that the $pp\to H^{\pm }{W}^{\mp }$ cross section can be resonantly enhanced by up to an order of magnitude over its MSSM value (both for $\sqrt{s}=7\mathrm{TeV}$ and 14 TeV) through the contributions of heavy, neutral, singlet-dominated Higgs bosons appearing in the $s$-channel. Since such Higgs mass configurations are normally not possible in the MSSM, the observation of associated $H^{\pm }{W}^{\mp }$ production at the LHC could provide a striking, although indirect, signature of a more complicated Higgs sector.

Using domain-wall lattice simulations, we study pseudoscalar-pseudoscalar scattering in the maximal isospin channel for an $SU(3)$ gauge theory with two and six fermion flavors in the fundamental representation. This calculation of the $S$-wave scattering length is related to the next-to-leading order corrections to $WW$ scattering in technicolor models through the low-energy coefficients of the chiral Lagrangian. While two- and six-flavor scattering lengths are similar for a fixed ratio of the pseudoscalar mass to its decay constant, six-flavor scattering shows a somewhat less repulsive next-to-leading order interaction than its two-flavor counterpart. Estimates are made for the $WW$ scattering parameters and the plausibility of detection is discussed.

A simple model of nonfemtoscopic particle correlations in proton-proton collisions is proposed. The model takes into account correlations induced by the conservation laws as well as correlations induced by minijets. It reproduces well the two-pion nonfemtoscopic correlations of like-sign and unlike-sign pions in proton-proton collision events at $\sqrt{s}=900\mathrm{GeV}$ analyzed by the ALICE Collaboration. We also argue that similar nonfemtoscopic correlations can appear in the hydrodynamic picture with event-by-event fluctuating nonsymmetric initial conditions that are typically associated with nonzero higher-order flow harmonics.

We present predictions for the production cross section of a standard model $Z^0$ boson in association with a $t\overline{t}$ pair at the next-to-leading order accuracy in QCD, matched with shower Monte Carlo programs to evolve the system down to the hadronization energy scale. We adopt a framework based on three well-established numerical codes, namely, the powheg-box, used for computing the cross section, helac-nlo, which generates all necessary input matrix elements, and finally a parton shower program, such as pythia or herwig, which allows for including $t$-quark and $Z^0$-boson decays at leading-order accuracy and generates shower emissions, hadronization and hadron decays.

Neutrino-electron scatterings ($\nu -e$) are purely leptonic processes with robust standard model predictions. Their measurements can therefore provide constraints to physics beyond the standard model. Noncommutative (NC) field theories modify space-time commutation relations, and allow neutrino electromagnetic couplings at the tree level. Their contribution to the neutrino-electron scattering cross section was derived. Constraints were placed on the NC scale parameter ${\Lambda }_{\mathrm{NC}}$ from $\nu -e$ experiments with reactor and accelerator neutrinos. The most stringent limit of ${\Lambda }_{\mathrm{NC}}>3.3\mathrm{TeV}$ at 95% confidence level improves over the direct bounds from collider experiments.

We have searched for the lepton-number violating processes $B^{+}\to h^{-}{\ell }^{+}{\ell }^{+}$ with $h^{-}=K^{-}/{\pi }^{-}$ and ${\ell }^{+}=e^{+}/{\mu }^{+}$, using a sample of $471\pm 3$ million $B\overline{B}$ events collected with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ collider at the SLAC National Accelerator Laboratory. We find no evidence for these decays and place 90%-confidence-level upper limits on their branching fractions $\mathcal{B}(B^{+}\to {\pi }^{-}{e}^{+}{e}^{+})<2.3\times {10}^{-8}$, $\mathcal{B}(B^{+}\to K^{-}{e}^{+}{e}^{+})<3.0\times {10}^{-8}$, $\mathcal{B}(B^{+}\to {\pi }^{-}{\mu }^{+}{\mu }^{+})<10.7\times {10}^{-8}$, and $\mathcal{B}(B^{+}\to K^{-}{\mu }^{+}{\mu }^{+})<6.7\times {10}^{-8}$.

We show that the differences between correlators of the critical $O(N)$ vector model in three dimensions and those of the free theory are precisely accounted for by the change of boundary condition on the bulk scalar of the dual higher spin gauge theory in ${\mathrm{AdS}}_4$. Thus, the conjectured duality between Vasiliev’s theory and the critical $O(N)$ model follows, order by order in $1/N$, from the duality with free field theory on the boundary.

We present the time-dependent solutions corresponding to the dynamical D-brane with angles in ten-dimensional type II supergravity theories. Our solutions with angles are different from the known dynamical intersecting brane solutions in supergravity theories. Because of our ansatz for fields, all warp factors in the solutions can depend on time. Applying these solutions, we construct cosmological models from those solutions by smearing some dimensions and compactifying the internal space. We find the Friedmann-Lemaître-Robertson-Walker cosmological solutions with power-law expansion. We also discuss the dynamics of branes based on these solutions. When the spacetime is contracting in ten dimensions, each brane approaches the others as the time evolves. However, for a $\mathrm{D}p$-brane ($p\le 7$) without smearing branes, a singularity appears before branes collide. In contrast, the D6–D8-brane system or the smeared $\mathrm{D}(p-2)-\mathrm{D}p$-brane system with one uncompactified extra dimension can provide an example of colliding branes (and collision of the universes), if they have the same charges.

Massive $Z^{\prime }$-gauge bosons act as excellent harbingers for string compactifications with a low string scale. In D-brane models they are associated to $U(1)$ gauge symmetries that are either anomalous in four dimensions or exhibit a hidden higher-dimensional anomaly. We discuss the possible signals of massive $Z^{\prime }$-gauge bosons at hadron collider machines (Tevatron, LHC) in a minimal D-brane model consisting out of four stacks of D-branes. In this construction, there are two massive gauge bosons, which can be naturally associated with baryon number $B$ and $B-L$ ($L$ being lepton number). Here baryon number is always anomalous in four dimensions, whereas the presence of a four-dimensional $B-L$ anomaly depends on the $U(1)$-charges of the right-handed neutrinos. In case $B-L$ is anomaly-free, a mass hierarchy between the two associated $Z^{\prime }$-gauge bosons can be explained. In our phenomenological discussion about the possible discovery of massive $Z^{\prime }$-gauge bosons, we take as a benchmark scenario the dijet plus $W$ signal, recently observed by the CDF Collaboration at Tevatron. It reveals an excess in the dijet-mass range $150\mathrm{GeV}/{\mathrm{c}}^2$, $4.1\sigma$ beyond standard modelexpectations. We show that in the context of low-mass string theory this excess can be associated with the production and decay of a leptophobic $Z^{\prime }$, a singlet partner of $SU(3)$ gluons coupled primarily to baryon number. Even if the CDF signal disappears, as indicated by the more recent D0 results, our analysis can still serve as the basis for future experimental search for massive $Z^{\prime }$-gauge bosons in low string scale models. We provide the relevant cross sections for the production of $Z^{\prime }$-gauge bosons in the TeV region, leading to predictions that are within reach of the present or the next LHC run.

We show that for an SU($N$) Yang-Mills theory the classical background-quantum splitting is nontrivially deformed at the quantum level by a canonical transformation with respect to the Batalin-Vilkovisky bracket associated with the Slavnov-Taylor identity of the theory. This canonical transformation acts on all the fields (including the ghosts) and antifields; it uniquely fixes the dependence on the background field of all the one-particle irreducible Green’s functions of the theory at hand. The approach is valid both at the perturbative and nonperturbative level, being based solely on symmetry requirements. As a practical application, we derive the renormalization group equation in the presence of a generic background and apply it in the case of an SU(2) instanton. Finally, we explicitly calculate the one-loop deformation of the background-quantum splitting in lowest order in the instanton background.

Cosmic strings with degrees of freedom beyond the standard Abrikosov-Nielsen-Olesen or Nambu-Goto strings are ubiquitous in field theory as well as in models with extra dimensions, such as string theoretic brane inflation scenarios. Here, we carry out an analytic study of a simplified version of one such cosmic string model. Specifically, we extend the velocity-dependent one-scale string evolution model to the case where there is a conserved microscopic charge on the string world sheet. We find that whether the standard scale-invariant evolution of the network is preserved or destroyed due to the presence of the charge will crucially depend on the amount of damping and energy losses experienced by the network. This suggests, among other things, that results derived in Minkowski space (field theory) simulations may not extend to the case of an expanding Universe.